Wafers are the core material for manufacturing semiconductor chips. They are generally round, thin sheets made of high-purity silicon. Transistors, capacitors, resistors, and multi-layer interconnect structures are constructed on their surfaces through processes such as photolithography, etching, and thin film deposition. Therefore, the quality of the wafer directly determines the performance of the chip.

Wafer processing is susceptible to temperature. Temperature fluctuations will affect the etching depth, photoresist development effect, and film stress distribution, thereby affecting the consistency of the microstructure. Therefore, the wafer fabrication must be equipped with a high-precision, fast-response, and long-term stable temperature control system. High-precision temperature control is essential equipment for the wafer fabrication.

Key Processes Using Semiconductor Chillers

Photolithography

Photolithography is a micro-pattern transfer technology that “prints” circuit patterns onto the surface of the wafer. Its process accuracy determines the integration and performance of the chip. The specific steps are to evenly spin-coat the photoresist on the wafer, expose it through a mask, expose a specific area to light, then use a developer to show the pattern, and finally solidify and dry it.

Chillers can control the temperature of the light source of the exposure machine, the process chamber of the spin coater, and the cooling plate of the developer. This prevents photoresist degradation and alignment errors caused by localized thermal expansion of the wafer. It can also provide cooling water for high-precision laser positioning systems.

Dry Etching

Dry etching is divided into reactive ion etching (RIE) and inductively coupled plasma etching (ICP). Use plasma or reactive gas to engrave the pattern formed by lithography into the material layer. In this process, the chiller is used to cool the reaction chamber, control the temperature of the electrode platform, and protect the vacuum pump system and plasma source. Its temperature control stability directly affects the verticality and uniformity of the etched pattern.

Thin Film Deposition

Deposition is the formation of an insulating layer, a conductive layer, or a barrier layer on the wafer. It is mainly achieved through physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). The chiller can control the temperature of the deposition reaction chamber, cool down the target, coil, cooling plate, and other parts, and avoid fluctuations in film thickness and the generation of particles. Among them, the ALD process requires higher temperature control accuracy, and dynamic temperature control can only be achieved with the help of a chiller.

Polishing process

Chemical mechanical polishing (CMP) is a process of polishing the wafer surface to achieve global flatness under the combined action of chemical corrosion and mechanical friction. This is a necessary step before multi-layer interconnect metal wiring. The circulation of the polishing slurry and the friction between the polishing pad and wafer generate significant heat. Failure to remove waste heat in time will cause thermal expansion of the polishing disc, affecting the flatness of the wafer surface. This requires a chiller to cool the polishing disc in time, control the temperature of the polishing liquid, and provide constant temperature pure water for the cleaning equipment after polishing.

Inspection and testing

After each process stage, defects and electrical properties must be detected through tests such as AOI automatic optical inspection, E-beam electron beam inspection, and electrical probe testing. The chiller helps cool the AOI lens, electrical probe seat, CCD, and laser scanning module to avoid image drift or error caused by equipment temperature rise.

Wafer fabrication requirements for chillers

The wafer fabrication’s requirements for chillers cover multiple aspects such as accuracy, stability, cleanliness, and response speed.

Temperature control accuracy

In processes such as lithography, etching, and thin film deposition, any slight temperature difference may cause line width changes, uneven film thickness, or differences in etching depth, affecting chip performance. Certain critical processes demand temperature precision of ±0.05℃ or even ±0.02℃.

Response speed

Process switching is relatively frequent in wafer manufacturing, and the chiller must be able to quickly adjust the temperature to prevent production delays. The chiller is required to quickly reach the set temperature and operate stably after startup. The heating or cooling rate should reach at least 5℃/min. Even if there is a temperature disturbance, it must be able to quickly return to the set value.

Cleanliness

The core workshop of the wafer fabrication is an advanced clean room, and even tiny impurities may be brought into the process, causing wafer contamination. Therefore, the chiller should use ultrapure water with a resistivity of > 10 MΩ·cm as cooling water to prevent ionic impurities from entering the cavity. The material used for the pipeline cannot have metal precipitation.

Stability

The wafer fabrication is usually open all year round. The equipment operation cost is high, and any failure of the chiller may cause batch defective products. The continuous operation time of the chiller is required to be greater than 20,000 hours, and it is equipped with dual pumps, dual circuits, or N+1 redundant design. It should support remote alarms, system self-diagnosis, automatic switchover, and other intelligent functions.

Zoned temperature control

There may be different process zones on a device, such as the heating zone and cooling zone, and coolants of different temperatures are required at the same time. This scenario generally uses a multi-channel chiller that can independently control the parameters of each flow channel. Each zone’s temperature, pressure, and flow rate can be set independently.

Safety

The process liquids used in wafer manufacturing may have characteristics such as flammable, toxic, or corrosive. Chiller units need to pass international certifications such as CE, UL, SEMI S2/S8, RoHS, etc. The electrical, refrigerant circuit, pump body, etc. should meet the explosion-proof requirements. The system should also be equipped with various safety devices.

LNEYA Semiconductor Chiller

LNEYA is a Chinese chiller manufacturer focusing on the research and development of high-end temperature control equipment. Its products are widely used in wafer manufacturing, packaging and testing, laser, chip packaging, and other links.

We provide customized chiller solutions with a controllable temperature range of -150℃ to +350℃ and a temperature control accuracy of up to ±0.02℃, with flexible configurations including multi-channel control, air-cooled or water-cooled options, explosion-proof designs, and more.

Discuss your wafer temperature control needs with LNEYA chiller experts.